1. Technical Field
The present invention relates to a light source device and a projector.
2. Related Art
A light source device and a projector which forms image light corresponding to image information by modulating light emitted from the light source device and projects the expanded image light on a projection surface such as a screen are known. A typical light source device of this type includes a discharge type arc tube such as extra-high pressure mercury lamp, and a reflection mirror for reflecting light emitted from the arc tube. In this case, the arc tube has high temperature at the time of light emission.
More specifically, the arc tube of the projector includes a substantially spherical light emission portion and a pair of sealing portions extending from both ends of the light emission portion in directions away from each other. The arc tube further includes light emission substance such as mercury sealed into the light emission portion. At the time of lighting of the arc tube having this structure, the temperature of the upper region of the light emission portion becomes the highest, and the temperature of the lower region becomes the lowest. When high temperature condition of the upper region of the light emission portion continues, devitrification is easily caused. Moreover, blacking is easily produced with increase in temperature difference between the upper region and the lower region. In this case, the arc tube easily deteriorates. Thus, the upper region of the arc tube needs to be cooled with high efficiency.
This type of projector is placed on an installation surface such as a desk in a normal position, or fixed to a ceiling or the like in a suspended position in the direction opposite to the normal position in the vertical direction. According to these installation positions, the area where heated air remains within the projector placed in the normal position is different from that area of the projector in the suspended position. Thus, in case of a structure including a flow path of cooling air for cooling the components of the projector as a path established before use, the light source device of the projector cannot be adequately cooled in the normal position or the suspended position depending on the installation condition. For overcoming this problem, a light source device capable of supplying cooling air to the upper region of the light emission portion by using an air direction changing plate rotatable by its own weight in both cases of the normal position and suspended position has been proposed (for example, see JP-A-2002-189247; FIG. 8).
According to the light source device disclosed in JP-A-2002-189247, cooling air for cooling the light emission portion is guided in a slightly downward direction by the air direction changing plate after flowing in a duct, and introduced into a reflection mirror (reflector) via air intake port and air supply hole. In this case, the cooling air cannot reach the arc tube with appropriate inclination, and thus cannot be adequately supplied to the upper region of the arc tube.